Seleucus II Callinicus in the context of "Achaeus (general)"

Achaeus (Ancient Greek: Ἀχαιός, Achaiós; died 214 BC) was a general and later a separatist ruler of part of the Greek Seleucid kingdom. He was the son of Andromachus, whose sister Laodice II married Seleucus II Callinicus, the father of Antiochus III the Great. He accompanied Seleucus III Ceraunus, the son of Callinicus, in his expedition across mount Taurus against Attalus I, and after the assassination of Seleucus III Ceraunus revenged his death; and though he might easily have assumed the royal power right then, he remained faithful to Antiochus III, brother of Seleucus III, for the time being, that is until he proclaimed himself king in 220 BC.

During a military engagement between Ptolemy III and Seleucus II, the precise circumstances of which are still unknown, his father Andromachus fell captive to Ptolemy III. Andromachus was eventually suggested to be a bargaining chip which would force Achaeus to join forces with Ptolemy against Seleucus, though at this stage Achaeus' loyalty was still unwavering.